Nonwovens
Every gram moved to meltblown buys barrier and costs tensile. Only finer meltblown escapes the trade.
— mbar
The barrier this split delivers
Both performance relations are linear fits and both have limits the linear form does not show. Hydrostatic head does not rise indefinitely with meltblown weight: below roughly two or three grams per square metre the layer has pinholes and delivers almost no head at all, so the linear model badly overstates thin barriers, and at the other end head saturates as the structure becomes effectively closed. Tensile is genuinely close to linear in spunbond weight over the ordinary range but depends on bonding calender temperature and pattern at least as much as on grams, and an over-bonded laminate loses tear while gaining tensile. Fit both constants on the actual laminate being made. The cost figure is polymer and conversion only and ignores the fact that meltblown output per line-hour is a small fraction of spunbond output, so the true marginal cost of a meltblown gram in a plant running near capacity is far above its material cost - which is usually the real reason a producer resists raising the share. Nothing here treats the alcohol repellency or the barrier-to-liquid-under-pressure that a medical specification actually calls for; hydrostatic head correlates with them but does not substitute for them.
SMS Layer Balance: Barrier Against Strength — free, with the formula and a worked example, at Textile School.